Control systems of external machines by a voice command have been developed in recent years. In a first conventional control system of an external machine by a voice command, a voice command is supplied via a microphone to the control system to control an external machine, and an operator of the control system is informed visually or aurally that the voice command is a accepted. If the operator confirms that the accepted voice command is a desired command, the operator supplies a confirmation signal to the control system to supply the machine with a command signal to controll, so that the machine is controlled to operate in accordance with the voice command. If the operator recognizes that the accepted voice command is not the desired command, the operator may not supply a confirmation signal, so that the machine may not be controlled to operate by the voice command.
In a second conventional control system of an external machine by a voice command, a command signal is supplied to an external machine after a predetermined waiting time passes upon the acceptance of the voice command, so that the machine is controlled to operate automatically unless an operator of the control system supplies a halt command to the system in the predetermined waiting time.
According to the first and second conventional control systems of external machines by a voice command, however, there are disadvantages as described below.
In the first conventional control system of an external machine by a voice command, it is troublesome for the operator to supply a confirmation signal every time the voice command is accepted, especially when the voice command is a desired one.
In the second conventional control system of an external machine by a voice command, after the operator judges whether the accepted voice command is a desired one or not, the operator must supply a halt command to the system in the predetermined waiting time, when the accepted voice command is not the desired one. Therefore, if the waiting time is set to be long, operation time becomes long. On the other hand, if the waiting time is set to be short, the operator is required to supply the halt command quickly.